Many commercial operations, including restaurants, nursing homes, hospitals, and laboratories, utilize large amounts of hard surface disinfectants and typically maintain a significant inventory of such products. As a consequence of that and the fact that commercial disinfectants are often manufactured and sold in large quantities, disinfectant products are often stored for long periods of time. They are stored in warehouses before they are shipped to customers and then they are stored again as part of the customer's inventory. Because it is known that certain quaternary amine-based disinfectant formulations tend to discolor (turn yellow) over time, and because customers expect (and demand) product stability, research efforts have been focused on development of a stabilized disinfectant composition which maintains its clarity and does not discolor during storage.
A number of researchers have focused on the use of didecyl dimethyl ammonium chloride and quaternary ammonium chlorides for use in germicidal compositions. See for example U.S. Pat. No. 3,836,669, and Kirk-Othmer Encyclopedia of Chemical Technology. The compositions, however, required the addition of ammonium sulfate to give the composition the clarity of water. They gained only limited acceptance in the market-place due to the noticeable ammonia smell left behind long after the composition was applied. Recognition of the market's desire for water-clarity along with the high volume use of hard surface disinfectants has provided significant incentive to develop water-clear disinfectant solutions lacking an offensive ammonia smell.
More recently other researchers have reported that water-clear germicidal compositions could be formulated without the addition of ammonium sulphate and with the addition of tetrasodium ethylenediamine tetraacetate. See for example U.S. Pat. No. 4,464,398. The tetrasodium ethylenediaminetetraacetate serves as a detergent builder. Further, tetrasodium ethylenediamine tetraacetate has been considered to be a necessary component of the formulation for its function to aid in the breaking down of the bacterial cell walls. Quaternary amine-based disinfectant compositions utilizing ethylenediamine tetraacetic acid ("EDTA") and sodium hydroxide, however, fail to maintain their clarity, and often discolor with or without the addition of dyes during storage. There remains, therefore, a significant need to develop a clear, color-stable, hard surface disinfectant which provides both the performance and appearance properties necessary to meet customer expectations.
According to the present invention, there is provided a disinfectant composition formulated to have improved color stability without compromising bacteriocidal activity. The composition comprises bacteriocidal quaternary amine compounds a non-ionic surfactant, water, and an alkali bicarbonate in an amount effective to retard discoloration of the composition.
Further in accordance with this invention there is provided a method for improving stability of quaternary amine-based disinfectant compositions by the addition of effective amounts of alkali bicarbonates.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention.